Fred Astaire delights us and the Roosevelts intrigue us.They were dismal years, the 1930s, yet we smile at them now.

We like the decade's films and fashions, the virile voice of Cagney, poignant Dust Bowl ballads, and cashmere-coated gangsters in long black cars. But our nostalgia is selective: We still scorn '30s art, wrongly, as stumbling and cautious, too political, provincial. So the rich display of art from the '30s now on exhibition at the National Collection of Fine Arts is a revelation.

That most thoughtful, least predictable of Washington's museums has marked the 50th anniversary of the start of the Depression not with one show, but with four important exhibits.

Almost all the works displayed were paid for by the government in one way or another, yet the heavy hand of Uncle Sam rests lightly on this art. These WPA cartoons, these oddly colored paintings, these muscled limestone horses, have about them something unexpected, free and touching. This is not propaganda; the art is moving, timid yet whole-hearted, grandiose yet grungy. One feels before these objects an old order dying and a new one being born.

The four shows support one another. They are "Sculpture and the Federal Triangle," "After the Crash," "Art of the Federal Recovery Programs 1933-1943," and "Prints for the People." Taken together, they trace a sort of stair. In the basement are the bargains, the inexpensive WPA prints produced for the masses. The many paintings on display seem somehow more ambitious. Above them are the statues, the eagles and urns, the pediments and heroes, that give the Federal Triangle its half-innocent, half-pompous semi-antique charm. All these works reflect something of the '30s, that doubtful and yet hope-filled devasted time.

The viewer who explores these shows feels old standards and values wither.Arts manners are seen in transition. The avant-gardists represented seem to pull back from experiment even as their foes, the academic painters, turn against high polish.

Andrew W. Mellon, the secretary of the Treasury who pushed through the completion of what astounding complex of bureaucratic buildings that stands north of the Mall, sought to make of Washington a capital as grand, as elegant and classical, as London, Paris, Rome. He both lost and won. The buildings completed in the '30s are rich with hand-carved ornament, statues and broad stairs, but the old official standards, the high beaux arts politeness that these works obey were already dying before the job was done.

The printmakers and painters here are battling with modernism, struggling to place their art on some less demanding ground, and yet modernism's shadow falls across them. The architects and sculptors remain loyal to old details, yet one feels blandness winning as the decade moves on.

Throughout the displays are an affection for the rough, a distrust of the too-polished, a preference for the gutsy that will burst into the drips and stains and splashes of the abstract pictures of the New York School. Too much sophistication was thought a bad thing in the '30s.

Joshua C. Taylor, the National Collection's director, has observed that in that decade "there was little or no bravado painting with brilliant technical display; pictorial eloquence in the 1930s was considered a mark of callousness and superficiality. A carefully maintained technical stammer suggested that the artist had more to say than the brush could articulate."

Sculptors, too, here avoid the overly refined. Their heroic postmen, their mighty-muscled workers and monumental animals take on, as the '30s end, an eerie sort of smoothness as if they have been ground down by poverty and struggle, the bracing, yet eroding, spirit of the time.

There is much in '30s art that is worth dismissing, and, perhaps, forgetting. The dullest of the pictures here are not free of pap. The dullest of the buildings where bureaucrats now work, Interior, for example, are as close to Albert Speer's as they are to those of antique Greece and Rome.

Understandably, perhaps, there is something gloomy, pompous and pretentious in the art of the period, but throughout these exhibitions one feels a kind of breezy joy, a shared concern, an innocence, a sense that art can strike a light that pushes back the dark.